For instance, Japanese Patent Public Disclosure No. 62-5357 discloses a conventional example of a dual-chamber type prefilled syringe comprising a cylindrical body provided at a leading end with a portion for attaching an injection needle, within which a first chamber and a second chamber are formed. More specifically, this conventional art, for example as shown in FIG. 6, hermetically fits a front plug member 52, a middle plug member 53 and an end plug member 54 within the cylindrical body 51 in the mentioned order from a leading end side thereof. Formed between the front plug member 52 and the middle plug member 53 is the first chamber 55 which accommodate a first component 56. Further, formed between the middle plug member 53 and the end plug member 54 is the second chamber 57 which accommodates a second liquid component 58. The cylindrical body 51 has an inner surface formed with a bypass 59 in the form of a concaved groove longer than the middle plug member 53, along an axial direction of the cylindrical body 51. When the middle plug member 53 moves toward the leading end side to reach a position where the bypass 59 is formed, the first chamber 55 communicates with the second chamber 57 via this bypass 59. It is noted that an injection needle 61 is attached to the portion 60 for attaching the injection needle at the leading end of the cylindrical body 51 and is covered with a protector cap 62. In addition, a plunger rod 63 is inserted through an opening at a rear end of the cylindrical body 51 and is detachably attached to the end plug member 54.
As for the conventional dual-chamber type prefilled syringe 50, when the end plug member 54 is moved to the leading end side while pressing the plunger rod 63, the middle plug member 53 is pushed and moved through the component 58 accommodated in the second chamber. This enhances an inner pressure of the first chamber 55 to result in moving the front plug member 52. The portion 60 for attaching the injection needle has an interior area provided with a plug accommodation chamber 64 which has an inner peripheral wall formed with concaved communication grooves 65. Thus if the front plug member 52 moves to enter the plug accommodation chamber 64, the first chamber 55 communicates with a liquid passage within the injection needle 61 through the communication grooves 65 and a gap between the front plug member 52 and an inner surface of the plug accommodation chamber 64. In this state, upon further pressing the plunger rod 63, the middle plug member 53 moves to reach the position where the bypass 59 is formed, thereby communicating the first chamber 55 with the second chamber 57 via the bypass 59. In consequence, the pressing of the plunger rod 63 allows the second accommodated component 58 to pass through the bypass 59 and enter the first chamber 55 to result in being mixed with the first accommodated component 56.
However, according to the foregoing conventional technique, at the initial stage of the communication effected between the first chamber 55 and the second chamber 57, the liquid second accommodated component 58 which passes through the bypass 59 possesses so large a kinetic energy that upon pressing excessively quickly the plunger rod 63, the second accommodated component 58 passes through the bypass 59 to vigorously splash out. As a result, part of the splashed out second component reaches the injection-needle attaching portion 60 to cause a likelihood that it flows into the gap between the front plug member 52 within the plug member accommodating chamber 64 and the inner surface of the plug member accommodating chamber 64 as well as into the communication grooves 65.
Once the second accommodated component 58 has entered the communication grooves 65 or the like, it cannot readily return into the first chamber 55. Accordingly, upon pressing the plunge rod 63 thereafter, the second accommodated component is pushed out with the air in the first chamber 55 to leak out of the leading end of the injection needle 61. As a result, the liquid second accommodated component 58 not only dirties or damages the surroundings of the dual-chamber type prefilled syringe 50 but also becomes insufficient in amount to disperse and dissolve the first accommodated component 56 to entail a fear of inappropriately dispersing and dissolving the first accommodated component 56 or the like.
The present invention has a technical object to solve the above-mentioned problems and to provide a dual-chamber type prefilled syringe which prevents part of a liquid component accommodated within a second chamber from passing through a first chamber to reach a portion for attaching an injection needle which is present at a leading end of a cylindrical body when the liquid component flows into the first chamber upon effecting an operation for communicating the first chamber with the second chamber.